P0B56 code meaning
Hybrid/EV Battery Voltage Sense F Circuit Low
Powertrain system Generic code P0Bxx codes Check engine light
What P0B56 means
The GM two-mode hybrids of 2012, Tahoe, Yukon, Escalade, Silverado and Sierra, show a detail of P0B56 that lithium-ion packs lack. Their nickel-metal hydride pack is read in blocks, channel F being block 6, and the battery pack control module sets the code only when block 6 and block 7 both read under 2 V in 15 of 20 samples at 100 ms, Type B, two trips; a shared sense wire between the blocks is the obvious suspect then. In GM's lithium-ion systems the battery energy control module uses 0.2 V or less on cell voltage F for 1.4 s within 2 s, Type A. In both cases the controller assumes a failed measurement and reduces battery use until repair.
P0B56 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyWorkshop only
- Typical labor0.3 to 6 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P0B56
- Hybrid system warning, MIL after the second drive (two-mode)
- Engine runs continuously, no electric launch
- Lower fuel economy
Common causes of P0B56
- Most likelyFault in the sense wire shared by blocks 6 and 7 (GM two-mode)
- PossibleChannel F sense line shorted to a neighbouring line
- PossibleFailed input on the cell monitoring electronics
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Hv battery voltage sense fWiring harnessBms
What each part of P0B56 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| B | Area: hybrid propulsion. |
| 56 | The exact fault in that area. |
What to do next
- Note P0B56 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P0B56
What does P0B56 mean?
P0B56 means "Hybrid/EV Battery Voltage Sense F Circuit Low". The GM two-mode hybrids of 2012, Tahoe, Yukon, Escalade, Silverado and Sierra, show a detail of P0B56 that lithium-ion packs lack. It is a generic code, so it means the same on every make.
Is it safe to drive with P0B56?
Drive gently and only to a workshop. With P0B56 the car can go into limp mode (reduced power) to protect itself.
Will P0B56 fail an emissions test?
Yes, it can. P0B56 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P0B56 to fix?
Difficulty: workshop only. A typical repair takes 0.3 to 6 hours of work. This is a job for a workshop.
Will P0B56 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.